JP3469261B2 - Diffusion bonded sputtering target assembly and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target assembly having a backing plate, and particularly to a target material having a melting point of less than 1000 ° C. such as aluminum or an aluminum alloy, and the target material and the backing. Plate and 10 μm
Having the above thickness and Ag, Cu, Ni and those
Target which is excellent in adhesion and bonding strength and has a crystal grain size of the target material of 250 μm or less, which is solid-phase diffusion bonded through an insert material selected from one or more kinds of alloys of It is about.

[0002]

2. Description of the Related Art A sputtering target is usually a disk-shaped plate which serves as a sputtering source for forming electrodes, gates, wirings, elements, protective films, etc. of various semiconductor devices on a substrate by sputtering. When the accelerated particles collide with the target surface, the atoms constituting the target are released into space by the exchange of momentum and are deposited on the facing substrate. As the sputtering target, Al or Al alloy target, refractory metal and alloy (W, Mo, Ti, Ta, Zr, Nb, etc. and their alloys)
Target, high melting point silicide (MoSi _x , WSi _x
Etc.) A target or the like is typically used, and the target is usually used in the state of an assembly bonded to a backing material called a backing plate for the purpose of supporting and cooling. The target assembly is attached to the sputtering apparatus, and the back surface of the backing plate is cooled to remove the heat generated in the target during operation. As the backing plate, metals and alloys having good thermal conductivity such as OFC (oxygen-free copper), Cu alloy, Al alloy, SUS (stainless steel), or Ti to Ti alloy are used.

Conventionally, a brazing method using a low melting point brazing material such as In or Sn alloy has been mainly used for bonding the target and the backing plate.

However, the brazing method using a low melting point brazing material has the following drawbacks: the melting point of the brazing material is 158 ° C. for In and 160-300 for Sn based alloys.
Since the temperature is as low as ℃, the bonding shear strength decreases sharply when the operating temperature approaches the melting point.
S less than 1 kg / mm ² and relatively high strength
Even the n-alloy system has a low melting point of ² to 4 kg / mm ² , and since it is a low melting point brazing material, the joint shear strength sharply decreases as the operating temperature rises. Pores (pores) remain on the joint surface between the target and the backing plate due to solidification shrinkage, and it is difficult to perform 100% joint rate bonding without unbonded portions.

Therefore, the input power during sputtering is limited to a low level, and when the sputtering power exceeding the specified value is applied or the cooling water is insufficiently controlled, the bonding strength decreases or the brazing material increases with the temperature increase of the target. Problems such as the peeling of the target occurred due to the melting of.

When a brazing material having a high melting point is used instead of the brazing material having a low melting point, the quality of the target may be adversely affected because a high temperature is required for brazing.

Recently, in order to improve the throughput during sputtering film formation, there is a tendency to use a larger input power during sputtering. Therefore, there is a strong demand for a target capable of maintaining the bonding strength at a predetermined level or higher even at a high temperature. ing.

Under these circumstances, JP-A-4-143268 and JP-A-4-143269 disclose a first metal member as a sputter material and a second metal member as a supporting portion thereof directly or with a first metal member. Disclosed are a target and a method for manufacturing the target, which are involved in a step of joining and integrating through a spacer having a melting point higher than that of a member. As an integration method, the explosive joining method (explosion welding method) is mainly explained,
In addition, it is described that a hot press method, a HIP method, and a hot roll method can be used. Taking the hot pressing method as an example, for example, Al-1% Si is used as the first metal member (sputtering material) and oxygen-free copper is used as the second metal member (supporting portion). Is processed into a relatively simple shape, and the two are bonded by hot pressing at a temperature of 300 to 550 ° C. for 60 minutes, a diffusion layer of about 2 μm is formed. After that, the joined first and second metal members (sputtering material and supporting portion) are each processed into a final shape. However, there is a description that the first metal member and the second metal member can be processed into a predetermined shape and then joined by the explosive welding method.

[0009]

However, the above-mentioned method is the first method under a very large impact or load such as the bombardment method, the hot press method, the HIP method and the hot roll method.
The second metal member is strongly pressure-bonded, and deformation of the first metal member (that is, the target material), which is the sputter material, internal strain and microstructure change accompanying it, and contamination of the surface layer are severe, and the final dimension shape is finished. It is not applicable to target materials. As described above, there is a description that the first metal member and the second metal member can be processed into a predetermined shape and then joined by the explosive deposition method. It is impossible to avoid structural changes and surface contamination.

In addition, in the above method, it is a serious problem that the crystal grain size of the target material becomes large. When the crystal grain size of the target material becomes large, the amount of sputter from the target material begins to fluctuate depending on the location of the target material because the crystal grain and the crystallographic orientation are different, and as a result, the film thickness varies, and thus the film characteristics tend to vary. It is sometimes pointed out as an important issue.

Recently, there has been a rapid increase in the number of cases in which wirings for semiconductor devices are produced by using a target material of less than 1000 ° C. such as aluminum or aluminum alloy,
Many of these target materials are supplied in very high purity and finished to final dimensions. With such a target material having a relatively low melting point, the target material is more damaged by the above method, and the crystal grain size of the target material is larger.

An object of the present invention is to provide a target material finished to a final size and shape having a melting point of less than 1000 ° C., while suppressing the crystal grains of the target material and without adversely affecting the target material such as deformation or deterioration, which is highly effective for a backing plate. It is to develop a technique of joining with strength.

[0013]

The present inventor has found that
For aluminum or aluminum alloy target materials having a melting point of less than, as a result of investigating a joining method that suppresses the crystal grain growth of the target material and hardly causes deformation or other adverse effects on the target material, the low temperature using the insert material It was found that the solid-state diffusion bonding in the above method can obtain a very good bonding between the target and the backing plate than expected. By performing diffusion bonding while maintaining the solid phase under a light load in a vacuum, high adhesion and high bonding strength without unbonded parts such as pores at the interface can be obtained without deformation of the target material. Moreover, the growth of crystal grains is suppressed.

The term "solid phase diffusion bonding" as used herein means that one or more kinds of insert materials are inserted between the target material and the backing plate, and the target and the backing plate are maintained in a solid state without being melted. This is a method of causing bonding at the interface under mild heating and pressurization conditions without causing adverse effects including crystal grain growth on the target material without causing adverse effects.

Based on this finding, the present invention provides (1) 1
Target material having a melting point of less than 000 ° C. and 10 μm
The target material, the insert material, the insert material and the backing plate are provided with an insert material having the above thickness and selected from one or more of Ag, Cu, Ni and alloys thereof, and a backing plate. , respectively, excellent adhesion and bonding strength, which has a diffusion bonding interface, the crystal grain size of the target material 250μm
Solid phase diffusion bonding a sputtering target assembly, wherein the or less, and (2) having a melting point below 1000 ° C., or more thickness 10μm and backing plate of the target material and a predetermined final shape of the predetermined final shape of the a and Ag, Cu, and inserted between the Ni and Louis concert material is selected from one or more alloys under vacuum 15
Temperature of 0 to 300 ° C and pressure of 1.0 to 20 kg / mm ² .
There is provided a method of manufacturing a solid-phase diffusion bonding a sputtering target assembly, wherein the crystal grain size of the target material, characterized in Rukoto to solid phase diffusion bonding with a force is 250μm or less. A typical example of the target material is aluminum or an aluminum alloy. Representative examples of insert materials are silver or silver alloys, copper and copper alloys, nickel and nickel alloys, and the like.

[0016]

[Function] The target material and the backing plate are 10 μ
having a thickness of m or more and Ag, Cu, Ni and it
The solid-state diffusion bonding at low temperature with the insert material selected from one or more of these alloys sandwiched suppresses the crystal grain growth of the target material, and the constituent atoms do not change or deform the target, High adhesion and high bonding strength are obtained by diffusing each other, and there is no sudden decrease in bonding strength due to increase in operating temperature. Since it is solid phase bonding, there is no unbonded part such as pores at the interface. Bonding with a highly reliable bonding rate is obtained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a sputtering target assembly which is diffusion bonded according to the present invention through a target material 1, a backing plate 2 and an insert material 3. Both are firmly bonded via the solid phase diffusion bonding interface 4. Moreover, the crystal grain size of the target material is 250 μm or less.

The present invention is directed to target materials having a melting point below 1000 ° C. Typical examples thereof are aluminum and aluminum alloys such as Al-Si-Cu, Al-Si, and Al-Cu. In addition, an alloy target containing a metal such as Cu or Au as a main component is also targeted.
The insert material in the present invention is usually Ag, C
u, Ni or alloys thereof may be used. One or more of these may be layered and used.

In producing the sputtering target assembly, the backing plate and the target are degreased and washed with an organic solvent such as acetone , and then 10 μm.
At least one insert material of Ag, Cu, Ni or an alloy having the above thickness is inserted into the interface. It is also necessary to degrease and clean the insert material. Physical <br/> why to use those 10μm or more thick as the insert material, in order to micropores caused by several μm of irregularities during machining remaining on the bonding surface of the target and backing plate remain This is because the bonding strength is reduced. The upper limit of the thickness of the insert material is not particularly specified as long as it can bring about solid phase diffusion bonding, but an excessively thick material is useless. Conventional foils, thin sheets, etc. can be used. As the material of the insert material, from the viewpoint of the melting point and the diffusivity which are appropriately high to bring about solid phase diffusion bonding, as described above,
Ag, Cu, Ni or alloys thereof are suitable. The insert material may be used by stacking one or more layers. It is important to prevent oxides and the like from existing on the joint surface.

A laminated body of a target material, a backing plate and an insert material is generally heated to a temperature of 1.0 to 1.0 at a constant temperature within a bonding temperature range of 150 to 300 ° C., preferably 150 to 250 ° C. under a vacuum of 0.1 Torr or less. 20 kg / mm
^Under a pressure of ² , preferably 3-10 kg / mm ² ;
A sputtering target assembly is obtained by diffusion bonding in the solid state. In order to prevent the formation of oxide, it is preferably carried out in a vacuum atmosphere of 0.1 Torr or less. The applied load is selected depending on the joining temperature and the target material. A minimum load of 1.0 kg / mm ² is required to press the interface so as to cause diffusion, while a load exceeding 20 kg / mm ² may cause damage to the target material. Also, the bonding temperature is 150 to 300.
The reason for setting the temperature to 150 ° C. is that if the temperature is lower than 150 ° C., the diffusion of atoms is insufficient and good adhesion cannot be obtained.
This is because the crystal grains of the target material grow when the temperature exceeds ℃. Further, the difference in the coefficient of thermal expansion between the target material and the backing plate is likely to cause warpage or distortion, resulting in a defective joint.

The sputtering target assembly thus obtained has a bonding interface of 100% bonding rate due to solid phase diffusion bonding which does not cause deformation or alteration of the target material and does not generate a liquid phase, and has a high input power. It can be used well in a sputtering apparatus. Moreover, the crystal grains of the target material can be suppressed to 250 μm or less,
Guarantees uniform sputtering. In order to reduce water and gas adsorbed on the target surface, unlike the case of low melting point brazing filler metal, the target itself is not
Baking at around ℃ is also possible.

Example 1 and Comparative Example 1 A 300 mm diameter Al-1% Si-0.5% Cu target and an OFC (oxygen-free copper) backing plate of the same size were ultrasonically degreased and cleaned with acetone. As the insert material, Ag foil having a thickness of 100 μm was used. After ultrasonic degreasing cleaning with acetone, an insert material was inserted between the Al-1% Si-0.5% Cu target and the OFC backing plate.

The Al-1% Si-0.5% Cu target, Ag foil, and OFC backing plate laminate were laminated under a vacuum of 5 × 10 ^-5 Torr with a bonding temperature of 250 ° C. and a load of 8 kg / mm ^2. Diffusion bonded. The crystal grain size of the target after joining was 150 μm.

Bonding shear strength at room temperature of test pieces cut out from five portions along the diameter of the diffusion bonding material and the conventional S
Same A jointed with n-Pb-Ag low melting point brazing material
FIG. 2 compares the bonding shear strength at room temperature of the laminated material of the 1-1-1 Si-0.5% Cu target and the OFC (oxygen-free copper) backing plate. FIG. 3 shows the temperature dependence of the bonding shear strength of these bonding materials. As shown in FIGS. 2 and 3, the bond shear strength at room temperature was Sn-Pb-A.
It is about 3 kg / mm ² using the g-based low melting point brazing material, but about 6 kg / m ² for the solid phase diffusion bonding material according to the present invention.
m ² and about twice as high as the joint shear strength, and in terms of temperature dependence, the joint shear strength is about 80 ° C., which is the melting point of the braze material, when the Sn—Pb—Ag-based low temperature braze material is used. Although it is zero, the solid phase diffusion bonding material of the present invention is 2
3 kg / mm ² or more at 00 ° C or higher, ² at 250 ° C
It holds the joint shear strength of kg / mm ² . FIG. 4 shows an Al-1% Si-0.5% Cu target according to the present invention,
The microscope picture of the junction interface vicinity of the laminated material of Ag foil and OFC backing plate is shown.

Example 2 When a target was produced by solid phase diffusion bonding using copper foil and nickel foil as insert materials in the same manner as in Example 1, the same effect was achieved.

(Comparative Example 2) In the same manner as in Example 1, solid phase diffusion bonding was carried out at a bonding temperature of 350 ° C, and the crystal grain size was 400 µm.

[0027]

Since solid-phase diffusion bonding is performed at a low temperature, the growth of crystal grains is suppressed, the target material is not damaged during fabrication, and the constituent atoms of the target material, the backing plate, and the insert material at the bonding interface are suppressed. Highly adherent and high bonding strength are obtained by mutual diffusion of each other, there is no sudden decrease in bonding strength with increase in operating temperature compared to low melting point brazing material, solid phase bonding Therefore, as a result that there is no unbonded portion such as pores due to solidification shrinkage of the brazing material at the time of bonding and a highly reliable bonding with a 100% bonding rate is obtained, (a) the target material that is finally finished is damaged. It can be bonded directly to the backing plate without causing (b) the uniformity of the sputtering is ensured, so that the film thickness becomes constant, which results in uniform film characteristics. (C) The input power during sputtering can be further increased, the throughput during sputtering film formation can be improved, and (d) the target itself can be baked at around 200 ° C. Further, it has an effect of reducing moisture and gas adsorbed on the target surface.

[Brief description of drawings]

FIG. 1 is a perspective view of a sputtering target assembly in which a target material and a backing plate are solid-phase diffusion bonded via an insert material according to the present invention.

FIG. 2 is a graph showing joint shear strengths at room temperature of a solid-phase diffusion bonding material according to the present invention and a bonding material using a Sn-Pb-Ag-based low melting point brazing material in Example 1 and Comparative Example 1 for comparison. is there.

FIG. 3 is a graph showing the temperature dependence of the bonding shear strength of the bonding material of FIG.

FIG. 4 is a micrograph showing a metal structure in the vicinity of a bonding interface of a laminated material of an Al-1% Si-0.5% Cu target, an Ag foil and an OFC backing plate according to the present invention.

[Explanation of symbols]

1 target material 2 backing plate 3 insert materials 4 Solid phase diffusion bonding interface

Continuation of front page (56) Reference JP-A-2-290968 (JP, A) JP-A-63-270459 (JP, A) JP-A 64-47863 (JP, A) JP-A-4-131374 (JP , A) JP-A-4-143268 (JP, A) JP-A-4-143269 (JP, A) JP-B-59-44956 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) C23C 14/00-14/58

Claims (4)

(57) [Claims] 1. A target material having a melting point of less than 1000 ° C., a thickness of 10 μm or more, and Ag, Cu,
An insert material selected from Ni and one or more of those alloys and a backing plate are provided, and the target material, the insert material, and the insert material and the backing plate are excellent in adhesion and bonding strength, respectively .
And has a diffusion bonding interface, solid phase diffusion bonding a sputtering target assembly which crystal grain size of said target material and wherein the at 250μm or less. 2. The solid phase diffusion bonding sputtering target assembly according to claim 1, wherein the target material is aluminum or an aluminum alloy. 3. The solid phase diffusion bonding sputtering target assembly according to claim 1, wherein the insert material is silver or a silver alloy. 4. A target material having a predetermined final shape and a backing plate having a predetermined final shape, each having a melting point of less than 1000 ° C., a thickness of 10 μm or more, and Ag, C.
u, solid at the temperature and pressure of 1.0~20kg / mm ² of 150 to 300 ° C. under vacuum with an intervening Ni and Louis down <br/> insert material is selected from one or more alloys thereof crystal grain size of the target material, characterized in Rukoto is phase diffusion bonding <br/> 25
A method for producing a solid phase diffusion bonding sputtering target assembly, which is 0 μm or less.